Getting stuck in

Written by: Justin Cunningham | Published:

Justin Cunningham talks to the adhesives companies that use customers as the catalyst for innovation

When we talk about innovation, many will not immediately think of adhesives. But, for those in the industry, sticking things together is a fixation.

One of the market leaders in bonding technology is Bracknell based 3M. The company originally started out as the Minnesota Mining and Manufacturing Company in the early 20th Century and continues to keep its headquarters in the US.

According to the company, you are never more than 10m away from a 3M product, and similarly, by the time you leave your house in the morning you'd have probably been in contact with about 25 of them.

Although the humble Post-It note is perhaps its best known mainstream product, it has developed a number industrial innovations such as VHB, very high bonding tapes. This is a foam tape with a pure acrylic adhesive core so it has high cohesive strength and it only needs a hand pressure to apply it.

It is innovations such as this that are changing the way designers can think about the assembly process as it offers a genuine alternative to mechanical fasteners.
More than ever, adhesives are replacing screws, rivets and welds in a number of industries from automotive to construction.

"The exterior panels of a lorry trailer are able to be bonded straight on to the support frame," says Edwin Eve, technical service manager for the Industrial Adhesives and Tapes Division at 3M. "The advantage of that is, it removes the need to drill, use screws and welds. And that reduces the potential for corrosion as well as vibration and rattles in the cab.

"It is also being used in construction by architects to seamlessly fix glass panels on to buildings. The tape is actually able to compensate for different rates of thermal expansion, so that is one less constraint for engineers when choosing the substrate materials."

VHB tape is viscoelastic meaning it stretches as it absorbs the force applied to the bond and then returns to its original shape. It is allowing many industries to rethink assembly processes and take out cost and improve quality, which has got to be a good thing particularly in the current climate.

It has also been able to help the automotive industry with its uptake of aluminium that is notoriously difficult to weld, by allow the materials to be bonding pieces together. It also expects to do similar things with the potential uptake of composites. It has already developed an adhesive from its experience with motorsport.

"We developed an adhesive called DP490 specifically for a customer in motorsport," says Eve. "Although the project itself was not the most rewarding financially, it was rewarding from a technical breakthrough perspective. That was something that, as a company, we wanted to do as we could see benefits further down the line."

And it has. As the use of composites has exploded in the aerospace industry, 3M has found that early adoption and initial unrelated research and development has paid off in dividends. The product already saw real testing on the track and just needed tweaking to take it forward into the aerospace sector.
"Innovation is just as much about a process and way of doing things as it is about developing a new product," says Eve. "It isn't so much about massive leaps forward but a lot of smaller steps, little bits of innovation that influence many other things further down the line."

But adhesives will never totally take over from fasteners. Although, there will always be screws, nuts and bolts, more and more design engineers are finding that actually adhesives can work better for them.

The reason is adhesives have better and quite often more attractive proprieties. The strength can be just as good, they are lightweight, do not suffer from vibration or fatigue, and can absorb quite a lot of energy, so can be used for noise dampening. And properties can be tailored for a particular function.

Although the process to apply them will have to be more tightly controlled, once that process is in place, there are lots of advantages. The obvious down side is the inability to disabled and reassembled, which is why nuts and bolts will always be necessary in some applications.

But again, "screws tend to have stress concentrations, localised build up of load around the holes and joins," says Eve. "Adhesives can distribute that load much more uniformly.

"We find that one of our main functions is getting out there and showing customers what the products can do and the potential for replacing traditional fasteners. We really want to get involved and know what the customer is after and find out what they actually want to achieve as the end result. That is key."

Similarly, Hemel Hempstead based Henkel has a parallel philosophy. "Really what we sell is solutions," says Henkel's marketing director Paul Marshall. "We actually use engineers as sales guys, to go out and visit factories to see where customers can improve processes, cut out costs or use our product more effectively."

Henkel is best known for its Loctite brand and it too supplies to diverse markets from offering rapid repair solutions for railway girders, to rapid UV curing adhesives for the medical industry.

With regards to convincing customers about the benefit of adhesives, the company often say that a physical demonstration is needed to prove its worth. "People often do not believe or know quite how well this stuff performs, and how much money it can save them," says Mike North, applications engineering manager at Henkel. "But you only need to give a demonstration for them to be convinced."

Quite often customers of Henkel will be familiar with its products and brands but not realise that it can remove processes, or get more out of existing products. Part of the issue comes down to educating the user.

"Design engineers might use adhesives to bond joints and although they use an adequate adhesive in terms of its properties, they can often miss the practical side, such the manufacturing guy actually applying it," says North.

An example of how Henkel has applied innovation to help its customers is the Pritt Stick style Threadlocker Stick. This is designed for manufactures applying the substance to bolts overhead. The Threadlocker has been made thixotropic meaning it is non-drip. That means the guys working with bolts overhead no longer have the substance drip down on to them if they use too much.

Another example of educating the user is with an engine designer. "They had a problem with a certain bolt that kept coming lose," says North. "These are very capable engineers, but they were applying the Threadlocker adhesive to a bolt that screwed into a threaded blind hole. As a result when the bolt was tightened, the air inside pushed some of the Threadlocker out, potentially causing a poor lock and seal. Instead they needed to apply the Threadlocker to the bottom of the blind hole, so when tightening the assembly, the adhesives is simply forced up around the threads, for a perfect lock and seal."

The company also sells an epoxy to the aerospace industry and has a special aerospace division based in Toulouse, to work with Airbus and its engineers. As the trend toward lightweight composites continues, an innovative Henkel breakthrough is continuing to help them make the most of the available technology.
It supplies epoxy film rolls that have to be stored at -80ºC. These are used to bond composite joints and cure inside the autoclave with the composite material itself.

But a recent innovation called, Epsilon resin, can be stored at room temperature. This simplifies processing enormously and substantially reduces the amount of wastage. Since cooling is no longer necessary, energy consumption in production is now much lower.

And the material is more heat resistant than the conventional material and also shows significantly higher strength and resistance. And since it absorbs less moisture in the course of its life cycle, the material has been shown to age more slowly as well.

Henkel spent five years researching the breakthrough in resins for composite materials. Currently specification trials are underway at all major aircraft manufacturers.

And another future development sees the company increasingly working with automotive designers to develop engine sealants' compatible with biofuels. One of the big topics is getting engines to be capable of using higher percentages of biofuel, which at the moment is limited to about 10% as it perishes the rubber seals and gaskets. North says: "That is a big area R&D focus area for us and something we are talking to the engineers at the OEMs about."

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